1. Field of the Invention
The present invention relates to soft magnetic films used as the core materials of thin-film magnetic heads. In particular, the present invention relates to a soft magnetic film which is composed of an FeCoα alloy, wherein α represents a noble metal, particularly FeCoRh, which has a saturation magnetic flux density Bs of at least 2.0 T, and which exhibits high corrosion resistance. Also, the present invention relates to a thin-film magnetic head including the soft magnetic film, a method for making the soft magnetic film, and a method for making the thin-film magnetic head.
2. Description of the Related Art
In order to achieve higher-density recording, for example, a magnetic material having a high saturation magnetic flux density Bs must be used as a core layer of a thin-film magnetic head to increase the recording density by the concentration of the magnetic flux in the vicinity of the gap of the core layer.
A traditionally used magnetic material is an NiFe alloy. The NiFe alloy film is formed by electroplating using a continuous DC, and exhibits a saturation magnetic flux density Bs of about 1.8 T.
However, the higher-density recording anticipated in the future requires a soft magnetic film having a higher saturation magnetic flux density Bs then the NiFe alloy can satisfactorily provide.
Another soft magnetic material often used, other than the NiFe alloy, is an FeCo alloy. An FeCo alloy film having an optimized composition has a higher saturation magnetic flux density Bs than that of the NiFe alloy film. However, it also has the following problem.
In some configurations of thin-film magnetic heads and other magnetic elements, an NiFe alloy film is disposed on the FeCo alloy film, which is formed by electroplating. Alternatively, FeCo alloy films are deposited on two faces of a nonmagnetic layer such as a gap layer, which is formed by plating. Unfortunately, these FeCo alloy films are often dissolved or corroded by ionization during the electroplating process.
It is likely that a large potential difference (standard electrode potential-difference), which is generated between the FeCo alloy film and the NiFe alloy film, or between the FeCo alloy film and the nonmagnetic layer, has a galvanic effect that dissolves the FeCo alloy film.
In a single FeCo alloy film configuration, this film must have a high corrosion resistance during the manufacturing processes of thin-film magnetic heads and other magnetic elements. For example, the film must have high corrosion resistance during the milling steps of sliders and the cleaning steps of the elements. Also, the film must have high corrosion resistance in the actual operating environments of thin-film magnetic heads.
Accordingly, soft magnetic films used in core layers of thin film magnetic heads must have both a high saturation magnetic flux density Bs and a high corrosion resistance.